1. Field of the Invention
The present invention relates to the field of semiconductor processing, and more particularly to the fabrication of waveguides for use integrated circuits containing semiconductor devices.
2. Discussion of Related Art
Transferring data by electricity within an integrated circuit has limitations in speed due to the heat produced. Also, the speed of transferring data by electricity is limited by the data rate. Therefore, the use of light to transfer data within an integrated circuit may be advantageous because light does not cause heat problems like electricity and light is also not limited by the data rate. In order to transfer data by light within an integrated circuit, waveguides take the place of the metal wires used to transmit electricity. Waveguides may be formed with any material that will transmit light from one point to another. The waveguides within an integrated circuit are surrounded by a cladding material to trap the light within the waveguides so that the signal is not lost after entering the waveguide.
One method of forming waveguides is illustrated in FIGS. 1a-1e. In FIG. 1a, a substrate is provided on which the waveguides and the integrated circuit may be formed. On this substrate 110, a first layer of dielectric material 120 is deposited. This layer of dielectric material 120 will serve as part of the cladding of the waveguides. Above the layer of dielectric material 120, a layer of waveguide material 130 is deposited at FIG. 1c. The waveguide material 130 can be any type of material that will transmit light with minimum light loss through the waveguide. The waveguide material 130 may have a rough top surface 135 after it is deposited. At FIG. 1d, the waveguide material 130 may be etched with an anisotropic dry plasma etch to form waveguides 140. The waveguides 140 may have sidewall roughness 145 after the anisotropic dry plasma etch. Over the waveguides 140, as illustrated in FIG. 1e, a second layer of dielectric material 150 is deposited to complete the cladding surrounding the waveguides 140.
The waveguides 140 formed by the above method do not transmit light very well. This is because the intensity of the incident light 160 that enters the waveguides 140 will be reduced by the sidewall roughness 145 and rough top surfaces 135 of the waveguides 140. The end light 170 that exits the waveguides 140 is much diminished in intensity. Therefore, the signal carried by this light will be noisy and the signal will be weakened due to a discrepancy between the initial light intensity and the final light intensity.